At the Station Casinos you do not need to swipe first for the senior multipliers. Just swipe and accept the multipliers anytime that day, before during or after you play. I tested this today to be sure.
On the other hand, as you said, we must swipe first to get the Boyd senior multipliers.
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From: mm4vegasvp@yahoo.com
You do need to swipe first to 'activate' these bonus multipliers on the day you play. (at least at the Boyd properties, and Stations). I think so. Points may be automatic, but I always swipe at the Kiosk first, anyways, as an infreq visitor - to check balances/promos etc.